Model Overview

We estimate the age of a site by calculating the years since the last fire. We then fit a curve to model the recovery of vegetation (measured using NDVI) as a function of it’s age. An additional level models the parameters of the negative exponential curve as a function of environmental variables. This means that sites with similar environmental conditions should have similar recovery curves.

Input data

The model was last fit on 2023-07-13 21:21:27.

This version of the model was fit with 10909 pixels including data from 2000-10-31 to 2014-06-26.

Workflow

This repository was developed using the Targets framework.

[1] “Loading libraries” ── Attaching core tidyverse packages ──────────────────────── tidyverse 2.0.0 ── ✔ dplyr 1.1.0 ✔ readr 2.1.4 ✔ forcats 1.0.0 ✔ stringr 1.5.0 ✔ ggplot2 3.4.1 ✔ tibble 3.1.8 ✔ lubridate 1.9.2 ✔ tidyr 1.3.0 ✔ purrr 1.0.1
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Attaching package: ‘arrow’

The following object is masked from ‘package:lubridate’:

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[1] “Attempting to install needed packages” [1] “Sourcing files” Loading required package: abind Loading required package: sf Linking to GEOS 3.10.2, GDAL 3.4.1, PROJ 8.2.1; sf_use_s2() is TRUE [1] “Setting options” [1] “setting time windows” cmdstan installation found, skipping installation

Results

Environmental Drivers

These parameters represent the relationship of the following environmental variables to the recovery trajectory.

Recovery Trajectories

The plot below illustrates some example recovery trajectories. It currently just shows the top 20 cells with the most observations.

Model Performance

Compare estimated vs observed values for all pixels. This is not true validation - these pixels were included in the model fitting.

Spatial Predictions

Maps of spatial parameters in the model.

Park Reports

See the links below for park-level reports on vegetation status.

Addo-Elephant_National_Park Agulhas_National_Park Bontebok_National_Park Garden_Route_National_Park Karoo_National_Park Namaqua_National_Park Richtersveld_National_Park Table_Mountain_National_Park Tankwa-Karoo_National_Park West_Coast_National_Park